I tried posting this earlier, but for some reason it wouldn't post to the form. I got my first octopus roughly three weeks ago. I don't know what species he is, but there is a picture of him while I was acclimating him below. He is in a 50 gallon tank with 80 lbs of live rock in it, and the tank has been cycling for ~6 months. It's set up with a Coralife Portien Skimmer, a 10 gallon sump under the tank (Biggest that would fit) which is fed by a homemade overflow which feeds into a filter sock sitting in the sump, then to the return pump, a 950 GPH Mag Drive pump. The return line has a branch off back into the sump to bleed off the flow to the tank without restricting the pump. The Protein Skimmer is set up inside the sump. Because there is so much live rock, I haven't been able to see him except for a fleeting glance when I turn the tank lights on in the morning . He had been eating snails and ghost shrimp for the first week, but I switched over to fiddler crabs and he has been eating those well, although he still likes to eat my snails. He has been very reclusive and hides all day, hunting during the night, or at least I think! Still haven't decided on a name, but I was wondering if anybody could get a good ID on him. When I got him he was about 3 cm Mantle with 8-9 cm legs (Both rough estimates). DWHATLEY: Apologies for taking so long to reply. We try to make a good guess as soon as we see a new octo post but between our new software upgrade pains and my personal internet (lack of) crisis suggestions have been slow. Do you know where this little one came from? I am guessing nocturnal pygmy but many look alike, especially in photos. The general look and Mantle:arm ratio would be consistent with the Caribbean Octopus mercatoris but we have not seen a lot of them in the last few years (more this last year than in several years prior where they were very common in the trade 5 or so years ago. Unfortunately, if I am correct, you won't likely see much of this one in a 50. My best suggestion is to place a cluster of Giant Purple barnacle ( search ebay using: 161024262084 link for reference only, these prices are exceptionally high. If you are in FL, check the tourist places - they are very common and imported but be sure they are not painted or varnished) shells about 1/3 of the way up the water column, embedded stably in your rock work. Finding a small cluster with a variety of sizes is often best (and some will be shaped to place the too large group on the bottom substrate to elevate the smaller, more desirable sizes). For no known reason, mercs seem to like these for dens (they are not native to FL) and will often take them and allow you to have viewing rights. If you try this keep a variety of shells (the empty snail shells will work) available to use as a door. JasonRashall: No need to be sorry on the delay, I had enough trouble posting this myself! Do you think that a 20 gallon would be better suited for him? I have one that has been cycling since may 30th, and reads 0 ammonium and 0 nitrates with a bio load of 6 damsels and 3 shrimp. The livestock could easily be caught, and I know where the octopus hides so he could be transferred easily as well. Here is a video of him during acclimation: http://youtu.be/cwgXjNCw-eQ DWHATLEY Still can't add to the thread but have reported it specifically. Until I saw your video I would have said yes to the smaller tank but have a bit of reservation now. I have never seen one quite that active in a large tank (in a bucket yes but not often and not the dwarfs). I am hoping this is not a California species that needs colder water. I still think its dwarf and a 20 (sans fish) would give you more viewing time without crowding the but be sure it is well sealed and lower the water level at least an inch if you can. The reason I worry about it coming from a colder environment is the look of the skin when it was out of the water. I have noticed (with VERY limited observation) that the colder water animals take on a slime sheen out of the water and actually feel a little slimy in the water. This is not the case with the Caribbeans (at least while they are alive). The activity level is not merc like but makes me think of some of the descriptions of O. digueti. I don't think I could easily tell them apart but I have never kept one. On the other hand sometimes phones show faster than life activity (that still does not cover the sheen though). You might try to keep the temp no higher than 74. Not a great solution but one that should allow a Southern CA animal to live and not be too cold for a Caribbean.